Recently, a wire known as a 0.3 sq wire having a conductor with a cross-sectional area of about 0.3 mm2 has been proposed. Since this wire is made lightweight and is thin in diameter in comparison with a normal wire, the wire is used in a complicated circuit portion or used as automotive wire to contribute to the achievement of an improvement in fuel efficiency (for example, refer to PTL1 and PTL2).
Here, a conductor in which a thin copper alloy is subjected to work hardening by a fine wire process (plastic working by drawing with a die) to promote strength improvement is used in such a wire. The thin copper alloy refers to an alloy in which alloy elements are added to copper within the solid solubility limit thereof.
In addition, in recent years, in order to achieve a lighter weight and thinner diameter, a 0.22 sq wire having a smaller cross-sectional area of a conductor than that of the 0.3 sq wire has been proposed (refer to PTL2).